What happened to Pull Request Titles?

Previously (2.12) a Pull Request Title would be based on the branch name. Now it seems to be based on the number of commits:

if 1 commit, the title becomes the commit message

if 2 or more commits, the title becomes the branch name

I can't seem to find a JIRA ticket associated with this change.. Can someone provide that to me so I can understand why this was changed, and if there's a way to turn this off so that it goes back to the original behavior.